A quantitative three-dimensional analysis of posterior facet displacement in Sanders Type II and III intra-articular calcaneal fractures.

OBJECTIVE

To quantify the three-dimensional (3D) displacement characteristics of the posterior facet fragment in Sanders type II and III intra-articular calcaneal fractures (IACFs) caused by falls from height, thereby providing a quantitative anatomical reference for reduction planning.

METHODS

We retrospectively analyzed CT data from 71 patients with closed Sanders type II/III IACFs. Mimics and 3-matic software were utilized for 3D reconstruction and simulated reduction. The translational and rotational changes of the fragment's geometric center were measured before and after reduction.

RESULTS

Significant displacement occurred in all directions (P < 0.05). Predominant translations were lateral (4.55 ± 3.16 mm) and inferior (3.81 ± 3.13 mm), while posterior translation was minor. Primary rotational deformities included axial plane internal rotation (17.62 ± 14.57°) and sagittal plane anterior tilt (12.29 ± 13.42°). Coronal plane varus (4.61 ± 13.97°) was minimal but exhibited high variability, indicating significant instability.

CONCLUSION

Posterior facet fragments primarily displace inferolaterally with significant internal rotation (∼17.62°) and anterior tilt. These findings suggest that rotational malalignment, particularly axial-plane internal rotation and sagittal-plane anterior tilt, may be an important but easily overlooked component of posterior facet displacement. The results may provide a quantitative anatomical reference for preoperative planning and intraoperative assessment of reduction, although further biomechanical and clinical validation is required.